Image of the Day: The Milky Way’s Mysterious “Infinity Sign”


The European Space Agency's Herschel Space Telescope provides an infrared view of a twisted ring at the center of our galaxy. The mystery is: how the ring got twisted. The origins of the structure of galactic centers are not well understood, but astronomers suspect that our Milky Way's shape may have been affected by gravitational interactions with nearby galaxies — perhaps including the Andromeda Galaxy, our big celestial neighbor.

"This is what is so exciting about launching a new space telescope like Herschel," Sergio Molinari of the Institute of Space Physics in Rome said. "We have a new and exciting mystery on our hands, right at the center of our own galaxy."

Molinari is the lead author of a research paper on the twisted ring, appearing in a recent issue of Astrophysical Journal Letters. Portions of the ring have been spotted before, but Herschel's image cuts through the dust at the galactic center to reveal the full structure in submillimeter wavelengths. This version of Herschel's view highlights the shape of the ring, which stretches across more than 600 light-years.

"We have looked at this region at the center of the Milky Way many times before in the infrared," said Alberto Noriega-Crespo of NASA's Infrared Processing and Analysis Center at Caltech, one of the paper's co-authors. "But when we looked at the high-resolution images using Herschel's submillimeter wavelengths, the presence of a ring is quite clear."

Astronomers say the ring is a dense, twisted tube of cold gas mixed with dust — and a cradle for infant stars. They used readings from the ground-based Nobeyama Radio Observatory in Japan to determine how fast gas was circulating around the ring. The radio observations showed that the ring is rolling as a unit, at the same speed as the rest of our galaxy.

The center of the twisted ring does not correspond with the actual center of our galaxy, a supermassive black hole known as Sagittarius A*. Noriega-Crespo said it's not clear why the centers don't match up.
"There's still so much about our galaxy to discover," he said.

The Daily Galaxy via ESA / NASA / JPL-Caltech


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